Near- and mid-infrared fiber lasers at the ∼2µm wavelength range are essential for applications such as medical diagnostics, environmental monitoring, and military confrontation. However, developing materials that provide both anti-crystallization stability and high gain in this range remains challenging. This study presents the development of high-gain Tm3+-doped barium antimony germanate (BaO−Sb2O3−GeO2, abbreviated as BSG) glass fiber, designed to achieve laser emission at 1.8–2 µm. Based on the glass-forming region, the composition of BSG bulk glass is optimized, and it exhibits a high Tm3+ doping concentration (N=3.3×1020ions/cm3), excellent anti-crystallization stability (ΔT=250∘C), and a large emission cross-section (σ e =8.4×10−21cm2). Tm3+-doped BSG optical fibers are fabricated using a melting–quenching method with a large full width at half-maximum of up to 200 nm in their amplified spontaneous emission spectra. Such Tm3+-doped BSG fibers produced gain coefficients of 6.48 dB/cm at 1950 nm and 6.03 dB/cm at 1867 nm when pumped at 1570 nm, respectively. Furthermore, laser outputs of 1862 nm and 1964 nm are achieved using a 2 cm long Tm3+-doped BSG glass fiber, highlighting the potential of BSG glass fibers in near- and mid-infrared laser applications.
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